The frequency of input or output (referred to as “input/output” hereinafter) signals provided to integrated circuit devices (ICs) has steadily increased over time. As the frequency of input/output signals reaches radio frequency (RF) ranges and approach the gigahertz range, complex impedances at the input/output node often result. The complex impedance of an IC input/output node can create impedance matching issues between the source of the input/output signal and the input/output node of the IC. Impedance mismatches can degrade performance of the input/output node, if not the IC in general.
Complex impedances are a function of multiple small capacitances and inductances associated with devices coupled to the input/output node of the IC. These small capacitance and inductances can include gate capacitances, inductances and capacitances associated with interconnect lines, packaging bond wire inductances, capacitance associated with input/output pads, capacitances associated with electrostatic discharge structures, and the like.
An impedance mismatch between a source of an input/output signal and an input/output node of an IC results in inefficient delivery of signal power to the input/output node since a percentage of the power of the input/output signal is reflected back from the input/output node to the source of the input/output signal. In addition, an impedance mismatch leads to a reduction in bandwidth of the input/output node since the small inductances and capacitances become more significant at higher frequencies.
To avoid signal power loss, RF systems strive to create a purely resistive impedance at each RF input/output and RF output. To offset complex impedances at IC input/output nodes, matching networks can be implemented at input/output nodes of the IC that seek to cancel the complex impedances. Without matching networks, many IC input/outputs would be band limited with maximum operating frequencies well below the frequency range of a desired input/output signal.